Respiratory tract mucociliary clearance and mucous rheology will be studied simultaneously in adult pure bred beagle dogs. There have been several studies on tracheal mucociliary clearance and several on the rheology of mucus. However, there are no studies in the literature which present data relating the two. This study will employ the best available methods to collect mucus, evaluate its rheology parameters and measure tracheal mucociliary clearance rate as a means of determining the qualitative and quantitative relationships between the rate of clearance and the rheologic properties of the mucus. Specifically this study will: 1) Demonstrate the effects of various systemically applied chemical and pharmacologic agents and the state of hydration on mucociliary clearance. 2) Evaluate the effects of these factors on mucous rheology. 3) Relate clearance to rheology. 4) Develop a means of objectively evaluating the results of therapy directed toward the airways in respiratory tract disease. Mucous will be collected by the SKF "tracheal pouch" its rheology studied using Litt's microrheometer; and the clearance rate measured by the 99mTc method of Giordano and Morrow. These methods eliminate many of the problems which have plagued previous investigators. If this study is successful in relating rheology to clearance, the clinician would then have measurable parameters, i.e. viscosicity and elasticity with which he could make assumptions about the important physiologic process of tracheobronchial mucociliary clearance. The clinician could then assess the results of his therapy on an objective basis rather than on the subjective means which are currently being used.